Relative time dating definition

Most fossils occur beneath water because these conditions most commonly occur in and around water.

These necessary conditions also make it highly likely that fossils will form in sedimentary rocks, which is part of why fossils are so important in relative dating.

There are several important principles in relative dating, which we will discuss below.

Smaller marine organisms are also limited in geologic time because they are often sensitive to environmental changes making them a boom-and-bust kind of organism.

That is, they become abundant, and then their sensitivity to environmental changes causes them to become extinct.

Relative dating is an important topic in AP Environmental Science.

It is used to help identify what ancient environments looked like, when certain kinds of animals lived, and what changes have happened in a given environment over many years.

Index fossils can also be used to determine relative ages of nearby layers of sedimentary rocks.

Characteristic fossils belong to a period, but do not define the time period.

Fossils are of special importance in relative dating because they help scientists understand the ages of certain rock formations, as well as what kinds of organisms lived together at the same time. First, the organism must be rapidly buried and remain buried over time.

Next, oxygen deprivation, continued sediment accumulation, and the absence of extreme heat and pressure are needed in order to prevent the organism from being destroyed before it is fossilized.

They occur where layers of rock were either eroded away or never deposited and cemented in the first place.

Sometimes there is evidence that an unconformity has occurred; other times, there is no way of knowing if there is a break in the relative time scale.

However, since environments change over time, this is not a perfect way of determining geologic age.

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